Electrical transformers are commonly found as components within a power grid used for either “stepping up” or “stepping down” voltage of an alternating current to allow for more efficient transportation of electrical power within the power grid. Transformers alter the voltage of the alternating current flowing through it by inductively coupling two conductors housed within the transformer. Specifically, both of the conductors include coils that are individually wound about a core (e.g., a silicon steel core having high magnetic flux permeability), where each coil includes a specific number of turns or windings and the change in voltage of the current flowing through the two inductively coupled conductors is proportional to the ratio of turns of the coil for each conductor.
Due to the high amount of current flowing through the two conductors of the transformer, each conductor's coil is housed within a sealed chamber containing a coolant to prevent damaging critical components of the transformer, such as the insulation covering the individual windings for each conductor. For instance, transformers often include oil, such as mineral oil, within the sealed chamber to provide cooling to the inductively coupled conductors. In this arrangement, oil may be circulated from the chamber and through a heat exchanger to cool the oil so it may be recirculated back into the sealed chamber to further cool the conductors. Because the oil used in cooling the conductors is often flammable, an ignition source (i.e., a spark) within the sealed chamber may ignite the oil, causing it to rapidly heat and expand as it vaporizes, rapidly increasing fluid pressure within the chamber. For this reason, some transformers include a pressure relief valve (PRV) coupled to the chamber and configured to open in the event of an overpressurization of the chamber so as to reduce fluid pressure within the sealed chamber by releasing fluid from the chamber and to, for example, the surrounding environment. For instance, PRVs often include a spring having a stiffness corresponding to the amount of absolute pressure at which the PRV is meant to actuate. However, a period of time exists between the overpressurization event (i.e., spark and subsequent ignition) and the complete actuation of the PRV, which is sometimes referred to as the “response time” of the PRV. Other transformer systems include a depressurization fluid circuit coupled to the transformer that contains a burst disc that is configured to burst or rupture when exposed to a predetermined differential pressure across the upstream and downstream faces of the disc. Traditional electrical transformer systems using PRVs and/or burst discs may have a response time of up to one second. Thus, the response time of the PRV/burst disc may allow fluid pressure within the sealed chamber to rapidly increase to a level that jeopardizes the physical integrity of the chamber, which may lead to an explosion of the sealed chamber. Further, in the case of transformer systems using burst discs, the depressurization system that includes the burst disc must be disassembled in order to install a new, un-ruptured burst disc before the transformer system may be operated again. The process of disassembling and reassembling such a system in order to replace the destroyed burst disc may be costly and time consuming.
Thus, there is a need for a depressurization system for relieving fluid pressure within a fluid filled sealed chamber of an electrical transformer. Such a mechanism would be particularly well received if it had a relatively swift response time that decreased the risk of an explosion in the event of an overpressurization of the sealed chamber.